1. Field of the Invention
The present invention pertains to vibration devices used for therapeutic purposes, and pertains particularly to such devices utilizing dual vibrator motors operating at different frequencies.
2. Description of the Prior Art
Vibratory devices are known using rotary members with eccentric weights. For example, such devices are disclosed by U.S. Pat. Nos. 3,124,125; 3,812,848; 4,059,110; and German Pat. No. 1,276,870. Also, U.S. Pat. No. 4,224,931 to Nelkin discloses a vibrating apparatus which utilizes a motor mechanically attached to dual vibrating arms to provide an enhanced vibratory effect.
Additionally, it is known from U.S. Pat. Nos. 3,653,375 and 4,105,024 to provide furniture with two vibrating motors vibrating or rotating at different frequencies to impart interference waves into the rigid furniture frame. However, none of the known prior art devices is suitable for imparting interference or beat frequency vibrations into small body massage appliances not having a rigid frame structure. Furthermore, prior art interference wave producing devices such as that shown in the aforementioned U.S. Pat. No. 3,653,375 require relatively complex control systems to regulate the amplitude and frequency of the beat frequency oscillations. The deficiency is exacerbated in body massage appliances since it has been found that a low massaging cycle rate on the order of one cycle per second is pleasing and advantageous to the user and such low rates are not known in small, light weight body massage appliances. Consequently, further improvements in such vibration devices are desirable and are provided by the device of the present invention.
It is an object of this invention to provide a vibrator appliance capable of producing beat frequencies or interference vibrations in any desired structure.
It is another object of this invention to provide a beat frequency body massage appliance for imparting massaging vibrations to selected body parts.